100-TW sub-20-fs Ti:sapphire laser system operating at a 10-Hz repetition rate

We developed a compact three-stage Ti:sapphire amplifier laser system that produced peak power in excess of 100 TW for a pulse duration of less than 19 fs and an average power of 19 W at a 10-Hz repetition rate. A final 40-mm-diameter Ti:sapphire amplifier is pumped by a Nd:YAG master-oscillator-power-amplifier system that produces ~7-J output of 532-nm radiation. The spatial beam quality is approximately 2 times diffraction limited for the full amplified compressed output pulse. With f/3 optics, this system should therefore be capable of producing a focused intensity of ~3x10(20) W/cm(2) .     

Sub-10-fs, terawatt-scale Ti:sapphire laser system

A three-stage, 1-kHz amplifier system delivering pulses shorter than 10 fs with a peak power in excess of 0.3 TW is reported. Passive and active spectral intensity and phase control allows the preservation of a bandwidth of 120 nm (FWHM) to as high as multimillijoule energy levels and temporal compression of the broadband pulses close to their Fourier limit. The system is scalable to peak powers well beyond 1 TW and holds promise for substantially advancing the state of the art of coherent laboratory soft-x-ray sources.     

Compression of the pulses of a Ti:sapphire laser system to 5 femtoseconds at 0.2 terawatt level

High intensity contrast ratio, pre-pulse free pulses with pulse duration of 5 fs and pulse energy of 1 mJ were generated at a repetition rate of 1 kHz by compressing the output pulses of a multi-stage Ti:sapphire laser amplifier system in a Ne-gas-filled hollow fibre. The spatial and temporal properties of the output laser beam were fully characterised. PACS 42.60.Jf; 42.65.Re; 42.81.Qb     

Measurement of thermal lensing in a power amplifier of a terawatt Ti:sapphire laser

We have measured detailed thermal lensing in a power amplifier of a terawatt Ti:sapphire laser operating at 50 Hz. The thermal lensing in the amplifier was evaluated by measuring the optical path difference (OPD) using a Shack–Hartmann-type wavefront sensor. It was found that the radial dependence of the OPD was almost quadratic in the pumping region, despite inhomogeneous pumping. Therefore, a simple spherical lens or convex mirror effectively compensates for the thermal lens in our amplifier. We found that the thermal lens profile was temporally stable, and did not degrade the pointing stability of the amplified laser pulses. We also found that the time constant of the thermal distortion in our power amplifier was approximately 0.5 s. Received: 3 September 2001 / Revised version: 23 January 2002 / Published online: 14 March 2002     

Passively mode-locked 10 GHz femtosecond Ti:sapphire laser

We report a mode-locked Ti:sapphire femtosecond laser emitting 42 fs pulses at a 10 GHz repetition rate. When operated with a spectrally integrated average power greater than 1 W, the associated femtosecond laser frequency comb contains approximately 500 modes, each with power exceeding 1 mW. Spectral broadening in nonlinear microstructured fiber yields comb elements with individual powers greater than 1 nW over approximately 250 nm of spectral bandwidth. The modes of the emitted comb are resolved and imaged with a simple grating spectrometer and digital camera. Combined with absorption spectroscopy of rubidium vapor, this approach permits identification of the mode index and measurement of the carrier envelope offset frequency of the comb.     

High power all-solid-state quasi-continuous-wave tunable Ti: sapphire laser system

This paper reports a high power, all-solid-state, quasi-continuous-wave tunable Ti:sapphire laser system pumped by laser diode (LD) pumped frequency-doubled Nd:YAG laser. The maximum tuned output power of 4.2 W (797 nm) and tuned average power of 3.7 W were achieved when fixing the Ti:sapphire broadband output power at 5.0 W and applying 750-850 nm broadband coated mirror.     

Wavelength swept Ti:sapphire laser

In this study, we demonstrate, for the first time to our knowledge, electronic wavelength sweeping of a continuous wave Ti:sapphire laser using an acousto-optic tunable filter (AOTF). The dependence of the laser output on the sweeping frequency and on the spectral tuning range was investigated. The lasing up to maximum scan rate 11 kHz for 10 nm tuning range and 5 W pump power was achieved. We detected and quantified asymmetry in the output for opposite scan directions. We theoretically characterized the maximum sweeping frequency for swept lasers with AOTFs and confirmed calculated results by measurements.     

20TW超短脉冲激光装置的研制

 介绍了基于啁啾脉冲放大技术的20TW全钛宝石超短脉冲激光装置的研制。该装置的主放大器采用全像传递的空间四程放大构型，可以保持良好的近场分布和提高能量转换效率。主放大器的钛宝石晶体为30mm×15mm，6台调Q倍频的YAG激光器泵浦。压缩后脉宽50fs，能量1J，峰值功率可达20TW，聚焦功率大于3×10¹⁸W/cm²。     

Wavefront correction of Ti:sapphire terawatt laser with varying precision of phase conjugation between deformable mirror and wavefront sensor

The phase conjugation between the deformable mirror and the wavefront sensor in the aberration correction of a terawatt Ti:sapphire laser is studied experimentally and theoretically in this paper. At varying values of phase-conjugation precision, we focus the corresponding beams into spots of the same size of 5.1 μm×5.3 μm with a f/4 parabola in the 32 TW/36 fs Ti:sapphire laser system. The results show that the precision of conjugation can induce an intensity modulation but does not significantly affect the wavefront correction.     

125-TW Ti:sapphire/Nd:glass laser system

We have demonstrated a Ti:sapphire/Nd:glass laser system that produces up to 51 J of energy in 395-fs pulses (125TW). Focusing at f/3 to a 2.5-times diffraction-limited spot results in a peak irradiance greater than 10(20) W/cm(2) . Our 40-cm-diameter gold diffraction gratings have a damage threshold of 0.42 J/cm(2) for 320-fs pulses.     

A femtosecond self-mode-locked Ti:sapphire laser with high stability of pulse-repetition frequency and its applications

The spectral characteristics and stability of a frequency of intermode beats of a fs self-mode-locked Ti:sapphire laser are investigated. An active method is used to obtain high stability. The frequency stability of intermode beats not lower than 1.27×10⁻¹² rms in 50 s is achieved. Possible applications of the setup, such as measurement of large frequency intervals in the optical range, creation of optical frequency synthesizers, etc., are proposed. The physical principles for the creation of an optical clock of a new type using a highly stable fs Ti:sapphire laser are considered. Received: 7 May 1999 / Published online: 27 October 1999     

Noise characterization of an all-solid-state mirror-dispersion-controlled 10-fs Ti:sapphire laser

We characterized the phase and amplitude noise of a mirror-dispersion-controlled 10-fs Ti:sapphire laser pumped by a frequency-doubled cw diode-pumped Nd:YVO₄ laser and compared with these of the Ti:sapphire laser pumped by an Ar-ion laser. The rms timing jitters and rms amplitude noise for the all-solid-state and Ar-ion laser pumped Ti:sapphire lasers are calculated to be 0.31 ps rms and 0.71 ps rms and 0.15% rms and 0.32% rms, in the frequency range from 20 kHz to 400 kHz, respectively. The phase and amplitude noise characteristics of the Ti:sapphire laser were greatly improved by using the diode-pumped solid state laser as a pump source.     

Generation of 16-fs, 10-TW pulses at a 10-Hz repetition rate with efficient Ti:sapphire amplifiers

We describe a two-stage Ti:sapphire amplifier laser system that is capable of producing 16-fs pulses of 10-TW peak power at a 10-Hz repetition rate. Thin solid etalons were used to control gain narrowing and gain saturation during amplification. A cylindrical mirror expander was used to permit compensation of the dispersion of the system. An efficiency greater than 90% of the theoretical maximum for conversion of 532-nm pump light to 790-nm radiation is demonstrated.     

TW级钛宝石飞秒激光放大装置中的同步控制

讨论了TW级飞秒激光放大装置中的同步时序系统原理,介绍了自行设计并建造的3套频率成分各异的TW级钛宝石飞秒激光放大装置,其中“极光Ⅱ” 和“Titan”为两级放大系统,前者预放大与主放大重复频率均为10 Hz,后者采用1 kHz的预放大和10 Hz的主放大,“极光Ⅲ”为多级放大系统,预放大重复频率为10 Hz,主放大分别为1 Hz和15 min输出一发。针对各个放大装置的不同特点和对同步精度的具体要求,自行设计并建造了不同的同步时序控制系统,实现了各个激光放大系统的有效运转,同步精度达到200 ps。     

Performance of gain-switched all-solid-state quasi-continuous-wave tunable Ti:sapphire laser system

We have made a gain-switched all-solid-state quasi-continuous-wave （QCW） tunable Ti：sapphire laser system, which is pumped by a 532 nm intracavity frequency-doubled Nd：YAG laser. Based on the theory of gain-switching and the study on the influencing factors of the output pulse width, an effective method for obtaining high power and narrow pulse width output is proposed. Through deliberately designing the pump source and the resonator of the Ti：sapphire laser, when the repetition rate is 6 kHz and the length of the cavity is 220 mm, at an incident pump power of 22 W, the tunable Ti：sapphire laser from 700 to 950nm can be achieved. It has a maximum average output power of 5.6W at 800nm and the pulse width of 13.2 ns, giving an optical conversion efficiency of 25.5% from the 532 mn pump laser to the Ti：sapphire laser.     

Laser-induced damage of high reflectors for Ti:sapphire laser system

A broadband (～ 176 nm, R ＞ 98%, λ0 = 800 nm) and high laser-induced damage threshold (LIDT =2.4 J/cm2) TiO2/HfO2/SiO2 high reflector (HR) for Ti:sapphire chirped-pulse amplification (CPA) laser system is fabricated by the electron beam evaporation. The refractive index and extinction coefficient of TiO2 and HfO2 films are calculated from single-layer films' transmittance spectra. The properties of HR are mainly determined by the high refractive index material. The high refractive index leads to wide bandwidth. A low extinction coefficient indicates low absorption and high LIDT. The possible damage mechanism of HR is discussed.     

TW级钛宝石飞秒激光放大装置中的同步控制

讨论了TW级飞秒激光放大装置中的同步时序系统原理,介绍了自行设计并建造的3套频率成分各异的TW级钛宝石飞秒激光放大装置,其中"极光Ⅱ"和"Titan"为两级放大系统,前者预放大与主放大重复频率均为10 Hz,后者采用1 kHz的预放大和10 Hz的主放大,"极光Ⅲ"为多级放大系统,预放大重复频率为10 Hz,主放大分别为1 Hz和15 min输出一发。针对各个放大装置的不同特点和对同步精度的具体要求,自行设计并建造了不同的同步时序控制系统,实现了各个激光放大系统的有效运转,同步精度达到200 ps。     

Self-starting Ti:sapphire holographic laser oscillator

We demonstrate, for the first time to our knowledge, operation of a holographic laser oscillator that uses laser-pumped Ti:sapphire (Ti(3+) : Al(2)O(3)) as the gain medium. The device is self-starting and self-adaptive by virtue of spontaneous gain-grating formation. We present experimental results of the system that include gain-switched pulses of 25-60-ns duration in a TEM(00) mode and as much as 11 mJ of output energy from a plane output coupler and 47 mJ from an intracavity polarizer port.     

SILEX-I: 300-TW Ti:sapphire laser

Based on chirped pulse amplification technology, we have built a Ti:sapphire laser system, called SILEX-I (superintense laser for experiments on extremes), at CAEP, which consists of three stages with 5-, 30-, and 300-TW outputs, respectively. The first and the second stages work at 10 Hz, while the third works at single shot. Pulse durations of 30 fs have been obtained by installing an acousto-optic programmable dispersive filter (AOPDF) to compensate for the spectral gain narrowing in the regen. By taking a number of advanced measures for spatial beam control, such as spatial beam shaping, relay-imaged propagation, precise alignment of compressor gratings, and OAP, near-diffraction limited focal spots (FWHM) have been obtained. Focused intensities are calculated at (1–3) × 10²⁰ W/cm² with an f/2.2 OAP.SILEX-I has shown an excellent stability and reliability in operations for applications since its completion and will soon be able to operate at 500 TW.     

All-solid-state high-peak-power Ti:sapphire laser system above 5-kHz repetition rate

We have developed an all-solid-state Ti:sapphire laser system, which produces 22-fs, 0.2-TW pulses at 5-kHz repetition rate. An average power of 22.2 W is the highest ever obtained in ultrashort laser sources. The serious thermal lensing due to high power pumping in a small area of Ti:sapphire crystal is controlled successfully by a stable quasi-cavity with two concave mirrors. The attempt to increase the repetition rate to 10 kHz is also described.